ABSTRACT
Reactions of indium and silicon with lithium nitride in Ca/Li flux produce two new nitridosilicates: Ca8In2SiN4 (orthorhombic, Ibam; a = 12.904(1) Å, b = 9.688(1) Å, c = 10.899(1) Å, Z = 4) and Ca3SiN3H (monoclinic, C2/c; a = 5.236(1) Å, b = 10.461(3) Å, c = 16.389(4) Å, ß = 91.182(4)°, Z = 8). Ca8In2SiN4 features isolated [SiN4]8- units and indium dimers surrounded by calcium atoms. Ca3SiN3H features infinite chains of corner-sharing SiN4 tetrahedra and distorted edge-sharing H@Ca6 octahedra. Optical properties and band structure calculations indicate that Ca8In2SiN4 is a void metal with calcium and indium states at the Fermi level and Ca3SiN3H is a semiconductor with a band gap of 3.1 eV.
ABSTRACT
Two new tellurium-containing nitrides were grown from reactions in molten calcium and lithium. The compound Ca6Te3N2 crystallizes in space group R3Ì c (a = 12.000(3)Å, c = 13.147(4)Å; Z = 6); its structure is an anti-type of rinneite (K3NaFeCl6) and 2H perovskite related oxides such as Sr3Co2O6. The compound Ca6(LixFe1-x)Te2N3 where x ≈ 0.48 forms in space group P42/m (a = 8.718(3)Å, c = 6.719(2)Å; Z = 2) with a new stuffed anti-type variant of the Tl3BiCl6 structure. Band structure calculations and easily observable red/green dichroic behavior indicate that Ca6Te3N2 is a highly anisotropic direct band gap semiconductor (Eg = 2.5 eV). Ca6(LixFe1-x)Te2N3 features isolated linear N-Fe-N units with iron in the rare Fe(1+) state. The magnetic behavior of the iron site was characterized by magnetic susceptibility measurements, which indicate a very high magnetic moment (5.16µB) likely due to a high degree of spin-orbit coupling. Inherent disorder at the Fe/Li mixed site frustrates long-range communication between magnetic centers.
ABSTRACT
Two new complex main-group metal carbides were synthesized from reactions of indium, carbon, and a metal hydride in metal flux mixtures of an alkaline earth (AE = Ca, Ba) and lithium. Ca(12)InC(13-x) and Ba(12)InC(18)H(4) both crystallize in cubic space group Im3Ì [a = 9.6055(8) and 11.1447(7) Å, respectively]. Their related structures are both built on a body-centered-cubic array of icosahedral clusters comprised of an indium atom and 12 surrounding alkaline-earth cations; these clusters are connected by bridging monatomic anions (either H(-) or C(4-)) and allenylide anions, C(3)(4-). The allenylide anions were characterized by Raman spectroscopy and hydrolysis studies. Density of states and crystal orbital Hamilton population calculations confirm that both compounds are metallic.
